I just tried Digital Media Converter evaluation version and it looks great. I have a question - when I convert the files for the Sony PSP, the volume is low making it difficult to hear in public places.

Before starting the conversion, on the menu select Tools >> Video Effects, select 'Change Volume Level' and use the slider to increase the volume. You can preview the volume levels to make sure there is no distortion, then proceed with your conversion.

When the conversion is complete click Tools >> Export to PSP and Digital Media Converter will transfer your converted files to your PSP.